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Effect of nitrogen rates on 'Western' pecan tree development

Nunez-Moreno, J. H., Walworth, J., Pond, A., Kilby, M.
Acta horticulturae 2018 no.1217 pp. 103-110
Carya illinoinensis, alternate bearing, boron, chlorophyll, copper, irrigation, leaves, mineral content, nitrogen, nitrogen content, orchards, pecans, trees, zinc, Southwestern United States
Annual application of nitrogen (N) at rates of 118 (118N), 236 (236N), and 354 (354N) kg ha-1 were applied on 35-year-old 'Western' (= 'Western Schley') pecan trees (Carya illinoinensis (Wangenh.) K. Koch) to evaluate their effect on nut yield, growth and leaf mineral composition. The leaf N concentration was only affected by treatments in one season. The effect on mineral composition was minimal: only zinc (Zn), boron (B), and copper (Cu) were affected in one season. No differences in yield and nut quality were found. Cumulative deviations of yield (alternate bearing intensity) in four consecutive years were 37, 33 and 28% in treatments 118N, 236N, and 354N, respectively, with a significant linear response. Cumulative yield efficiency was similar in all treatments and varied from 124 to 136 g of nuts cm-2 of trunk cross sectional area of the trees from 118N to 354N, but differences were not significant. Reproductive characteristics including the percentage of fruiting shoot and fruits per cluster were not affected. The chlorophyll index varied little between treatments, from 50 to 52 SPAD in treatments. We found that N rates from 118 to 236 kg N ha-1 satisfied N needs for pecan in irrigated orchards in the southwest United States.